A COMPARISON OF THE ANTIMALARIAL ACTIVITY OF THE CINCHONA ALKALOIDS AGAINST PLASMODIUM-FALCIPARUM INVITRO

  • 1 June 1990
    • journal article
    • research article
    • Vol. 93  (3) , 153-159
Abstract
The effects of four major cinchona alkaloids: (-) quinine, (+)quinidine, (-)cinchonidine, and (+)cinchonine against Plasmodium falciparum FCQ-27/PNG were studied. The alkaloids were tested in vitro as either single alkaloids, racemic mixtures of stereoisomers, or as an equimolar combination of all four alkaloids. Results indicate (+)quinidine to be most effective and both (+)stereoisomers were more potent than the (-)stereoisomers. Inhibitory concentrations 50% (Ki) or racemic mixtures of stereoisomers were similr to those of the (+)stereoisomers alone. The Ki of four alkaloids in equimolar combination were similar to that of the (-)cinchonidine/(+)cinchonine racemic mixture. A total alkaloidal extract of Cinchona sp. was tested and compared with the pure alkaloids. HPLC analysis indicated that (+)cinchonine, (-)cinchonidine and (-)quinine were present in a ratio of approximately 1:1:2, respectively. The total alkaloid extract, with (-)stereoisomers predominating, was less effective than the four alkaloids in combination. The nature of the interaction between stereoisomers was investigated and appears to be one of addition.